The present invention relates to a conveying or hoisting boom system. In particular, the present invention increases the stiffness and the load bearing capacity of a conveying or hoisting boom system and attached pipeline by incorporating a composite reinforcement fiber matrix into its construction.
Boom systems offer a safe, cost effective and efficient method of lifting a load and reaching to a distant elevated position. Boom systems can be mounted on portable platforms such as trucks. Truck mounted booms are used as portable lifting and moving mechanisms, as well as to support piping for pumping liquids or semi-liquids (such as concrete, slurries, grout and industrial or waste material). Booms which support piping may be used in a variety of applications ranging from pumping concrete at construction sites to directing water onto upper stories of buildings. Boom systems typically have more than one boom section. Each boom section has a corresponding actuator assembly which supports and moves the boom section (for example by articulating or telescoping the sections).
Each boom section acts as a cantilevered beam (with no support laterally along its length). Booms are frequently subjected to work conditions where the loads supported by the boom system place significant stress and strain upon the boom sections. It is important that the boom sections have a sufficient load bearing capacity to perform such activities. Additionally, the boom systems can be subject to excessive vibrations and deflections which can interfere with safe and effective operation. Vibrations, deflections and flexural stresses are used as design criteria and serve to limit the operational reach of the boom systems.
In some applications, the booms must be articulated with a high level of precision to allow proper positioning of the boom and to avoid undesired contact (or impact) with external objects which can cause damage to the boom sections. Pipelines attached externally to the boom sections are particularly vulnerable to damage from contact with external objects. The required precise positioning of the boom is hindered by a condition known as xe2x80x9cboom bounce.xe2x80x9d Boom bounce is a periodic movement of the boom proportional to the flexibility and length of the boom and to the magnitude of the applied force. A force which is applied to the boom (particularly if applied at the unsupported distal end) causes flexing of the boom. When the force is released, the boom acts like a spring, oscillating around its equilibrium position. When the boom is subject to sudden acceleration or deceleration, the weight of the boom itself can cause an inertial force to be applied to the boom resulting in the above described xe2x80x9cboom bounce.xe2x80x9d It is important, therefore, for each boom section to be stiff enough to minimize boom bounce.
As mentioned, significant stress and strain can be placed upon the boom sections by the weight of the load being supported by the boom system. Additionally, the weight of the boom itself and any attached pipeline can cause stress and strain upon the boom sections. Therefore, while it is important that the boom have significant stiffness and load bearing capacity, it is equally important that the boom and attached pipeline have as little weight as is reasonably possible. The weight of a boom and pipeline at a boom section distal from the truck must be supported by the boom sections proximate the truck. Since each boom acts as a cantilever, the greater the weight of the boom sections, pipeline, and the load supported by the boom, the greater the moment generated by the boom with respect to the support system. A xe2x80x9cmomentxe2x80x9d can be defined as the product of a force and the distance to a particular axis or point. If the boom is extended horizontally, the weight of the boom is moved farther away from the center of gravity of the boom and support system creating a larger moment about the support system. The increased moment causes an increased likelihood that the boom and support system may become unstable from dynamic or static load and tip over. Therefore, any increase in weight, will decrease the stability and reach of a boom system. If a pipeline is attached to the boom system, it may be cantilevered from the end of a boom and must have the ability to support itself over a span, requiring the pipeline to be strong as well as lightweight.
Stress and strain causing forces can be applied to the boom in a number of ways. For example, when the boom contacts an external object, or an object is suspended from the end of the boom, an external force is applied to the boom. Alternatively, when the boom is subject to sudden acceleration or deceleration, the weight of the boom itself causes an inertial force to be applied to the boom (resulting in the boom bounce described above).
Any pipeline attached to the boom sections is typically used to pump liquids or semi-liquids under pressure (e.g. using piston style pumps). Typically, forces also act on the pipeline with each stroke of the piston. The resulting stress on the pipeline and boom sections is called xe2x80x9cline shock.xe2x80x9d The force from the line shock causes the fluid to push transversely and/or longitudinally in a cyclical fashion against the pipe (and therefore the boom), producing a force normal or axial to the longitudinal axis of the boom. In some styles of pumps, impulse loads can be imposed on the boom system due to initial pressures (i.e., pressures which occur when the pump is started) imposed in the system, such as with centrifugal pumps.
Currently, boom sections and piping are typically manufactured of metal (steel, aluminum, etc.). The problem with using metals is that they are limited in length and reach due to their heavy weight and elasticity. Typical metals used in past boom systems have had a modulus of elasticity which causes them to easily flex, at least partially resulting in the xe2x80x9cboom bouncexe2x80x9d discussed above. Previously, to add stiffness to the boom system, larger cross-sectional boom sections were used, adding weight to the boom system. It is problematic, therefore, to produce a boom system which has strength and stiffness as its material properties, while still being lightweight and affordable. Therefore, there is a need in the art for a system which allows for increasing the load capabilities of a conveying or hoisting boom and attached pipeline system to withstand forces applied to the systems without significantly increasing the weight of the system components.
The present invention is a boom system comprising a plurality of articulated boom sections. Each boom section has a longitudinal axis. A stiffening layer is attached to a surface of at least one of the boom sections, and extends within about ten degrees of parallel to the longitudinal axis of the boom section. The stiffening layer is formed of a fiber-reinforced composite material including a plurality of fibers and matrix material.